Elongated louvers such as vertically and horizontally oriented slates of the type used in window treatment assemblies are well known in the art and commercially available in a wide variety of designs. The formation of louvers usually occurs through a forming machine, such as but not limited to, an extruder which produces an elongated continuous louver from a hot melt thermoplastic material such as polyvinyl chloride (PVC) and the like.
The window treatment industry has recognized the desirability of forming a decorative pattern on at least one exposed surface of the louver. By providing various decorative patterns, various effects can be obtained so as to provide a wide variety of products which will appeal to the consumer, as well as satisfying various decorating goals. It has been known to form decorative patterns in a louver by embossing a desired pattern or other like indication in at least one exposed surface of the louver through the utilization of cooperative pairs of rollers engaging opposite surfaces of the louver. For example, Kierson, U.S. Pat. No. 5,311,814 discloses an assembly for forming or embossing a decorative pattern on at least one exposed surface of an elongated slat preferably of the type used in vertical blinds. The assembly includes a pair of driven rollers which are designed, dimensioned and configured to engage opposite sides of a slat immediately subsequent to its formation by a plastic extruder. The exterior surface of one of the rollers has a decorative pattern formed thereon, and when forced into confronting engagement with an exposed surface of the slat, the decorative pattern is transferred by an embossing technique. A similar embossing process for laminated plastic panels is disclosed in Wellen, U.S. Pat. No. 3,481,818.
In order to enhance the decorative appearance of the embossed louver, it is desirable to impart color to the louver. In particular, it has been desired to provide color in a predetermined pattern, for example, within the valley formed during the embossing process. One approach is disclosed in Lewicki, Jr., U.S. Pat. No. 3,887,678 by preprinting the substrate to be embossed with various colored ink in a predetermined pattern using conventional rotogravure printing processes. This process has rendered it extremely difficult, if not impossible, to provide alignment of the pattern on the embossing roll with the printed pattern on the substrate to be embossed. Hence, a mismatch between the two patterns is often noted which detracts from the appearance of the resulting product.
Ruppel, et al., U.S. Pat. No. 5,339,730 discloses a method for printing and embossing sheets of paper made of cellulose wadding and with two or more plies. The method discloses applying ink to one of the sheets as it travels around a first embossing roller prior to being bonded with a second sheet which passes around another embossing roller. The resulting printed pattern is sandwiched between the two sheets which are glued together.
Terwilliger, U.S. Pat. No. 4,112,189 discloses a process for multicolor valley printing and embossing of flooring material. The apparatus includes a rotatable embossing and printing roll having an engraved surface contour representing a decorative pattern to be embossed and printed on a sheet of flooring material. A plurality of rotatable pattern rolls are arranged in operative engagement with the surface of the embossing and printing roll. Each pattern roll is designed to receive a different color ink and to transfer the ink to a discrete surface area of the embossing and printing roll in a manner such that certain portions of the surface area thereof receive one color ink from a single pattern roll and other portions thereof receive overlapping layers of different color inks from at least two pattern rolls. The pattern rolls are formed with raised portions corresponding to predetermined discrete raised surface areas of the embossing and printing roll to which ink from such pattern roll is to be applied. From the foregoing, it can be appreciated that there is the requirement for maintaining proper alignment between the pattern rolls and the engraved surface of the printing and embossing roll. To accomplish this registration, the embossing and printing roll, the pattern rolls, as well as the inking rolls of the ink transfer system must all be operatively linked together by a gear train which is driven by a motor.
Snyder, U.S. Pat. No. 3,850,095 discloses an apparatus and method for embossing and valley printing of carpets with a hot melt ink. In the disclosed apparatus, hot melt ink is transferred from a pickup roll immersed in the liquefied hot melt ink to a transfer roll. From the transfer roll, the hot melt ink is transferred to a inking roll which is in operative engagement with a printing and embossing roll.
Portnoy, et al., U.S. Pat. No. 3,681,159 discloses an apparatus and method for producing a textured printed surface on rigid laminated boards by printing and embossing. Registration of the printed pattern and the embossed pattern is achieved by providing the printing and embossing rolls of identical diameter and driving them at identical rotational speeds from a single power source. Based upon this construction, there is no flexibility to accommodate any variations in the construction of the individual components of the apparatus or laminated boards which during operation of the printing and embossing operation may affect registration.
Other techniques known to effect registration between an ink pattern and an embossed pattern include the use of compensator rolls and phase change rolls. In the case of compensator rolls, a movable compensator roll is positioned between the printing and embossing assemblies over which the substrate to be printed and embossed passes. The compensator roll is displaced transverse to the straight line path of travel between the printing and embossing assemblies. This effectively lengthens or shortens the path of travel of the substrate between the printing and embossing assemblies to effect registration of the patterns. Phase change rolls, on the other hand, change the surface speed of the printing or embossing roll so as to be greater or less than the advancing speed of the substrate to be printed or embossed. Although this allows for effective registration, it suffers from the disadvantage of causing smudging of the printed ink or variations in the embossed pattern due to the differences between the surface speed of the printing or embossing roll and the surface speed of the substrate.
Accordingly, there is an unsolved need for further improvements in an apparatus and method for embossing and printing elongated substrates with registered patterns.